1. Field
The present disclosure is generally related to improving ventilation within railroad tunnels by using air baffles to increase relative movement of air in the tunnel annulus as a train passes through.
2. Description of Related Art
Freight trains are often used to transport goods. As freight trains pass through railroad tunnels, particularly at lower speeds, overheating and loss of power of one or more locomotives within the train, and/or stalling of the train, may occur. This may often be caused by at least one of two factors: (1) the “piston effect,” and (2) accumulation of heated engine exhaust, hot radiator air, and pollutant gases. The “piston effect”—also referred to as the plunger effect—is a result of displacement flow which is the bulk movement of air or gases in a space, such as by the action of a piston or plunger in a cylinder-like shape. In the case of a train moving through a tunnel, for example, a leading locomotive (i.e., piston) tends to push air in the tunnel (i.e., cylinder) ahead of the train, thereby creating this effect. This results in lower air pressure in the tunnel and a reduction in air speed along the train. Additionally, as the train moves through the tunnel, the locomotive unit(s) expel exhaust gases and heated radiator cooling air (waste heat) into the air above and alongside the locomotive unit(s)—an area also referred to as the tunnel annulus. Because the piston effect reduces the flow of fresh air into the tunnel annulus (alongside the locomotive unit(s)), the exhaust gases and heated radiator cooling air tends to accumulate in the tunnel alongside the locomotive unit(s), particularly in tunnels of long length, and may move along with the locomotive unit(s) at the same or near-same relative speed. This is a particular problem for long freight trains incorporating multiple locomotives, as the locomotives, especially those further back in the train, will be forced to intake that heated/contaminated air.
The combined result of these factors is that the locomotive(s) may experience overheating due to resulting excessive radiator water and engine lubricating oil temperatures, for example, with the locomotives thus de-rating in power output or sometimes losing traction power. Also, lower air pressure in the tunnel, as caused by the piston effect, means less fresh air is available for intake and use in engine combustion. This may result in the train stalling in the tunnel. Such stalling incidents cause train delays, as well as risks to employees or personnel called to correct the problem.
To address such problems, several methods have been tried. Most railroad tunnels in the U.S., Canada, and Mexico are non-ventilated; however, a small number of railroad tunnels are equipped with powered, stationary ventilation fan equipment mounted therein in the hopes of preventing such problems (see, e.g., U.S. Pat. No. 4,567,817). Russian Patent Document No. RU 2332571 introduced flaps attached to a locomotive for trying to moving air within tunnels. Tunnel exit “curtains” have also been tried, such as illustrated in U.S. Pat. No. 4,037,526 to Jaekle, assigned to Southern Pacific Transportation Company. However, such curtains have proved to be maintenance-intensive and have been used sparingly.